1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, a recording medium and a program for obtaining an image and performing processing thereon.
2. Description of the Related Art
In a conventional image processing apparatus such as a color photocopier or a color MFP, when a color copy is performed, images of R, G and B are obtained through three channels by a scanner unit, the RGB images are converted into a CMYK image by a printer unit, and the CMYK image is printed out therefrom.
When a monochrome copy is made with a color photocopier, after RGB images are obtained by a scanner unit, the RGB images are blended at a specific blending ratio to produce a monochrome image, and the monochrome image is output through a printer unit. The wording “specific blending ratio” means here a ratio of brightness of the elements of the respective colors, is represented with a ratio of RGB values or the like, and is set at a ratio so as to fit to visual properties of human eyes.
However, if the blending ratio is fixed, when a specific color, the brightness of which tends to increase, is subjected to a monochrome conversion, there arises the following problem. That is, the brightness value of the color occasionally becomes close to the brightness value of a sheet of paper on which the image is output and therefore, the color becomes thinner or disappears when a monochrome copy is made.
In order to solve the above problem, Japanese Patent No. 3401977 discloses an art in the specification thereof, in which the blending ratio can be set desirably when producing a monochrome image from a color image.
However, in the above-mentioned conventional art, when security dots that are intended to be invisible are included in an original to be scanned, there arises a problem that the dots become visible. As an example, a case where yellow that can hardly be seen by human eyes is used for security dots, is given. When an original including characters of thin yellow with a blending ratio, which is set to fit to the visual properties of human eyes, is copied in a monochrome, frequently, characters of thin yellow color may not be reproduced on the monochrome image. Then, when a user changes the setting of the blending ratio so as to be able to produce a monochrome image having a thinner yellow, the thin yellow characters on the original can be reproduced recognizably for human eyes on a monochrome image.
However, when an original including yellow security dots is copied into a monochrome at a blending ratio that deepens the yellow of the security dots, the security dots, which are invisible in the original, may occasionally become visible. In this case, the purpose of the security dots is reduced.
As described above, in the conventional art, when the blending ratio is adjustable to produce a monochrome image from RGB image, the security dots intended to be invisible may become recognizable. Therefore, conventionally, there has been a problem that it is difficult that forming a monochrome image has both of the requirements: increase of reproducibility of color on an original and reduction of visibility of security dots.
An object of the invention is to provide an image processing apparatus, an image processing method, a recording medium and a program capable of suppressing security dots from being reproducible visibly while enhancing reproduction of a color in an original specified by a user, in the process of forming a monochrome image from a color image.